Histology of multiple myeloma

Photomicrograph of bone marrow from patient with multiple myeloma.
Click to enlarge image.

Plasma cells from patients with myeloma are usually immature in appearance with distinct nucleoli, and perinuclear vacuolization. There are also often multinucleated plasma cells.

Immunohistochemical analysis can verify monoclonality.

The plasma cells produce monoclonal IgG or IgA that can be detected through a characteristic serum protein electrophoresis pattern. Eighty percent of the patients have a complete monoclonal Ig in the serum and most of them simultaneously produce light chains something that may cause so-called Bence-Jones proteinuria.

Types

Asymptomatic multiple myeloma/smouldering multiple myeloma

In smouldering multiple myeloma, the M-component is >30 g/l and/or plasma cells in bone marrow aspirate >10% without organ involvement related to myeloma or the presence of any specific biomarkers.

(Symptomatic) Multiple myeloma

In multiple myeloma, there is >10% monoclonal plasma cells in bone marrow aspirate or biops, or clonal plasma cells in biopsy from a plasmacytoma. In addition, there must be presence of organ injury related to multiple myeloma or any other selected criteria indicating the high risk of symptom development within a short period of time.

Solitary medullary plasmacytoma

In solitary medullary plasmacytoma, there is solitary bone destruction, with or without tumor, consisting of monoclonal plasma cells without other sign of multiple myeloma.

Plasma cell leukemia

Multiple myeloma where >20% of leukocytes in peripheral blood or >2 x 109/L of the nucleated blood cells are plasma cells.

Non-secretory myelomatosis

In about 1% of the multiple myeloma patients, there is no detectable monoclonal Ig. this is called (real) non-secretory myeloma.

Light chain disease

In 20% of multiple myeloma patients, only light chain is secreted by the plasma cells. These light chains can most often be measured in serum (FLC) and in urine (urinary electrophoresis).This type of myeloma is named “light chain disease”.

These light chains are toxic to the kidneys, therefore, many patients with this disease are referred to the hospital because of renal insufficiency. Patients referred to the hospital with renal insufficiency of unknown cause should be evaluated to exclude myeloma with measurements of light chains as described above (FLC and U-elfo).

AL - amyloidosis

One type of amyloidosis is associated with monoclonal plasma cell proliferative disease, AL-amyloidosis. The amyloid forming protein is larger or smaller N-terminal fragments of monoclonal light chain. These proteins are deposited in the tissue and affect organs. In this disease, there is often found a monoclonal component, either by serum protein electrophoresis, urine protein electrophoresis or by free light chains. Clonal plasma cells are found in the bone marrow, although the amount may be low. The same plasma cell clone may also cause myeloma, and the patients may therefore have both of these conditions at the same time as part of the same disease. Amyloidosis patients has a somewhat better prognosis than myeloma, but the variation is greater. Patients with affection of the heart have the worst prognosis.